Field of the Invention
The present invention relates to a zoom lens, for example, to a zoom lens suitable as an image pickup optical system to be used in an image pickup apparatus, such as a video camera, a monitoring camera, a digital still camera, and a broadcasting camera.
Description of the Related Art
As image pickup optical systems to be used in image pickup apparatus using image pickup elements, zoom lenses having high optical characteristics and a wide angle of view have been demanded. For example, zoom lenses to be mounted on monitoring cameras have been desired to achieve a small entire system and a wide angle of view that enables monitoring of a wide area with one camera.
Besides the above demands, in view of an increase in image quality of monitoring cameras, the monitoring cameras, which have had a standard definition (SD) image quality, have been demanded to have full high-definition (HD) or 4K in recent years, and zoom lenses having high resolving power have accordingly been desired. In addition, zoom lenses have been desired to have a small F number in order to satisfactorily take images under an environment with a small light amount.
In order to satisfy those demands, there has been known a three-unit zoom lens including, in order from an object side to an image side, a first lens unit having a positive refractive power, a second lens unit having a negative refractive power, and a third lens unit having a positive refractive power. In each of Japanese Patent Application Laid-Open No. 2002-131640 and Japanese Patent Application Laid-Open No. H4-324812, there is disclosed a three-unit zoom lens in which during zooming, a first lens unit is configured not to move, and a second lens unit and a third lens unit are configured to move along mutually different loci.
In order to obtain, with the three-unit zoom lens described above, high optical characteristics over the entire zoom range while achieving a small entire system and a wide angle of view, it is important to appropriately set refractive powers and the lens structures of the respective lens units, and the like. In particular, it is important to appropriately set the refractive power and the lens structure of the second lens unit, the refractive power and the lens structure of the third lens unit, movement amounts of the second lens unit and the third lens unit during zooming, and the like.